Apparatus for electrical control



A. s. FuscssA 2,4%,8413 i APPARATUS FOR ELECTRICAL CONTROL Filed sept. 9. 1956 2 sheets-sheet 1 Ar'ToRNEY.

0d. 8, 1946.' A, RlGGS l 2,498,813

APPARATUS FOR ELECTRICAL CONTROL Filed Sept. 9, 1936 2 Sheets-Sheet 2 :fm2-....5 f2

IN VEN TOR.

H@ e. 41ML? ATTORNEY r//0^ Patented Oct. 8, 1946 UNITED STATES PATENT OFFICE APPARATUS FOR ELECTRICAL CONTROL Alger S. Riggs, Washington, D. C., assignor, by

direct and mesne assignments, to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application September 9, 1936, Serial No. 100,017l

'7 Claims. 1

My invention relates broadly to a method of producing alternating current voltages of predetermined wave form, primarily for control purposes, as functions of rotational speeds, and more particularly to a method and apparatus for obtaining high degrees of stability and accuracy in control system for follow-up purposes.

One of the objects of my present invention is to provide a circuit arrangement for a follow-up control system in which a high degree of stability and freedom from hunt and surge is obtainable. Another object of my invention is to provide a circuit arrangement for a follow-up control system wherein the controlled object may be made to run in absolute agreement with the transmitted data.

Still another object of my invention is the provision of a synchronized control system in which a receiving device is made to follow a transmitting device in angular displacement with any predetermined amount of lag or lead which may be controllably selected.

A further object of my invention is the construction of an apparatus from which an alternating current voltage functional upon rotative speedmay be derived from a rotating system for control purposes without taking torque from the rotating system.

A still further object of my invention is the provision of an apparatus for producing an alternating current voltage, as a function of rotational speed, having freedom from commutator ripple which is present in generating equipment of conventional character.

Another object of my invention is the provision of means for producing an alternating current signal from a Selsyn data transmitting system, for control purposes, which is a function of the angular velocity of rotation of the Selsyn transm mitter without in any Way loading the Selsyn system by producing said voltage.

Other and further objects of my invention reside in the method and circuit arrangement for an electrical control system as set forth more fully in the specication hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a fundamental diagram by which the principle of operation of my device may be understood; Fig. 2 is a vector diagram explanatory of the circuit of Fig. l; Fig. 3 is a vertical sectional View through one form of phase changing controller constructed in accordance with my invention; Fig. 4 is a transverse sectional View taken on line 4 4 of Fig. 3; Fig. 5 is a vertical sectional view of another form of phase changing controller embodying my invention; Fig. 6 is a transverse sectional vView taken on line 6-6 of Fig. 5; Fig. 7 is a longitudinal sectional View taken through a combined phase changing controller and a Selsyn motor employed in the system of my invention; Fig. 8 is a perspective view of the rotor in the apparatus of my invention; Fig. 9 is a diagrammatic View showing the control system of my invention; and Fig. l0 is a detailed diagrammatic view showing the arrangement of the windings in my phase changing controller where it is desired to add a damping component.

My invention relates broadly to a method of producing alternating current voltages, primarily for control purposes, as functions of rotational speeds. In electrical control circuits utilizing am* plifier systems for the remote control of heavy objects, such as searchlights and guns, there is frequently a need for a device producing alternating current voltages as functions of rotational speeds.y A conventional commutator type generator is unsuitable for this `purpose because the ripple produced by the commutator may detrimentally affect the control circuits.

By the use of a device of the character described herein, a smooth alternating current voltage depending upon rotational speed may be produced. Moreover my device requires negligible driving torque, inasmuch as it is not a true gen,- erator, but a speed actuated phase changing controller.

Due to the negligible torque required to drive my device, it is practicable to utilize it for the production of alternating current voltages as a function of rotational speed where the taking of high driving torque may give rise to inaccuracies in the control system.`

For instance, in data transmitting systems operating from a so-called Selsyn system, the use designing an electrical control for positioning heavy objects which may be operated in exact agreement or synchronism at all speeds, i. e., mono-periodically.

My invention utilizes the so-called generator action of an induction type alternating current motor, and is best understood by reference to the operation of such a motor from zero speed up to its synchronous speed.

Referring to Fig. 1, which is a diagrammatic drawing of a two phase squirrel cage type induction motor, the windings L1 and Lz are arranged so that their flux axes are at relation to each other-consequently-when the rotor is at rest and an alternating current voltage is applied to the winding L1, which I term the primary, there is no voltage present at the terminals of L2, which I term the secondary winding. If now the rotor is revolved, its motion in the primary iiux produces a voltage due to rotation which is inductively conveyed from the rotor to the secondary coil Lz-this voltage is proportional to rotational speed up to the speed corresponding to synchronous speed and is 90 out of phase with the voltage applied to the primary winding L1. The vector diagram of Fig. 2 shows the phase relation of the terminal voltages of the machinethe vector representing e2 (the secondary, or speed voltage) is 90 from the primary voltage and varies in magnitude substantially as a linear function of speed, up to synchronous speed and reverses sign upon reversing direction oi7 rotation.

Though generator action is present in producing the secondary or speed voltage e2 it is also a fact that a corresponding motor action is present-any power taken from the winding L2 is supplied in reality from the power source connected to the primary L1, and not from the source of original rotation of the rotor.

In practical use of the device for control purposes it is sometimes objectionable for the motor component to be present, since once started the device tends to run as a single phase A. C. motor. The motor component may be reduced to a negligible quantity by electrically loading the secondary winding, and may be still further reduced by the dynamic braking action of the rotor in revolving in a D. C. eld.

In order to provide damping action for the device when required, I provide a separate winding upon the stator having a different number of poles than the A. C. windings as illustrated for example in Fig. and energized from a suitable source of D. C. power. For instance, in one form of my invention I have wound the A. C. windings for two pole and the D. C. damper winding for four pole-both windings in the same slots.

In electrical control circuits employing amplication, the secondary or speed voltage of the machine must have a high degree of wave forni purity-so that the ripple caused by the squirrel cage is seriously detrimental. In such cases I provide a rotor having laminated discs without slots and simulate the squirrel cage effect by a conductive sleeve pressed and/or shrunk over the laminated core. I show a rotor of such construction in Fig. 3. In some instances even .M

the rotation of the laminated portion of the rotor gives rise to production of detrimental wave form distortion, and to prevent this I provide a still further form of rotor consisting of a conducting sleeve rotatably mounted, with provision for the iron core corresponding to the rotor core remaining stationary with the stator of the machine, the construction is shown in Fig. 5. Where it is desired to provide a voltage functional upon the angular velocity (or rotational speed) of a "Selsyn data system I propose to directly connect and rigidly attach a device of the type shown in Fig. 5 to a conventional Selsyn type receiver or synchro motor, this I have shown in Fig. 7.

For purposes of illustrating the utility of my invention I show in Fig. 9 a circuit whereby a heavy object may be controlled in angular position from a Selsyn transmitter. The system possesses extreme stability at all speeds because the displacement control is augmented by the difference in speeds between the data angular velocity and the speed of the controlled member. Since the diierence between these two speeds represents the absolute rate of approach or recession from agreement between data and controlled member, a voltage resultant oi these two speeds provides means for production of dead-beat iollow-up action.

Referring to the drawings in detail, Fig. 3 shows one form of my device for producing a voltage proportional to rotative speed, composed of the laminated stator 1 having distributed windings I the stator is held by means not shown, between the end frames 8 and El. The rotor consists of the laminated core I5 which is pressed on the shaft i4; the laminated rotor core I5 is completely surrounded by the non-magnetic but electrically conductive cylinder or sleeve I6 which performs the function of the squirrel cage illustrated diagrammatically in Fig. l. The rotor shaft is supported in the bearings l I and l2, and a cap I3 is provided near the end of the shaft opposite the driving end. Fig. 4, having like parts similarly designated Fig. 3 is a transverse section at 4 4 of Fig. 3. In Fig. 4 the general means of locating the windings is illustrated, the coils lil being held in the slots by wedges i8 as in conventional motor practice. The rotor is free to revolve in the stator which it clears by the air gap shown at I1.

Fig. 5 is an improved form of my device in which the entire magnetic core is stationary, and having as a rotor only the conducting non-magnetic shell 24. Referring to Fig. 5, the stator core is made up of the laminated core 1, held between the end frames I9 and 2), and the laminated core 25 attached by the bolt 26 and nuts 21 and 28 to the frame 2t. The laminated core 25 is the counterpart of the rotor core I5 in Fig. 3. The spacer 30 holds the inner core 25 in correct relation to the main stator core The rotor consists of the conductive but non-magnetic cylinder 24 which is attached at 29 to the shaft 23 and supported on bearings 2| and 22. The construction shown in Fig. 5 provides a stationary magnetic structure composed of the main stator core 1 and the concentrically located inner core 25 with a double air gap l1 and lla in which moves the rotor 24. Fig. 6 is a transverse section of Fig. 5 on the line S- and clearly shows the concentric relation of the rotor 24, main stator core 'l and inner core 25.

Fig. '7 is a section of another form of my device which I refer to as a data speed responsive controller, composed of a device as shown in Fig. 5 directly connected to a Selsyn type of repeater motor. Referring to Fig. 7 the stator core 1 is held between the end frame 32 and the bonnet 3|; the inner core 25 is held by the bolt 26, and the nuts 21 and 23 to the end frame 32 and spaced therefrom by the spacer 3D. The rotor 24 is attached to the shaft 31 at 3B. The shaft 31 is mounted in the bearings 39 and 40 to rotate the rotor 24 and the rotor 34 of the Selsyn repeater motor. The Selsyn repeater motor is shown for purposes of illustration as composed of the stator 32 held between the end frame 33 and the bonnet 3| and the rotor 34 operating in the stator 32. A surge damping device as usually employed on Selsyn type repeater motors is shown at 3S.

Fig. 8 is a perspective view of the rotor 24 of Figs. 5 and 7.

Fig. 9 is a diagrammatic drawing of my present invention employed in an improved form of electrical control system for follow-up purposes in which the telescope 4| through the vcontrol system causes the searchlight 62 to be synchronously controlled in agreement with the telescope.

The hand crank 42 through the gears 43, 44, shaft 12, gears 45, 45a, shaft 14, gears 46, 41 and shaft 13 is adapted to drive the telescope 4| angularly. The shaft 12 also rotates the rotor 48 of the Selsyn type of transmitter B. The polyphase stator windings 49, 59, 5| of the transmitter are connected to the corresponding windings 52, 53, 54 oi a Selsyn type displacement voltage controller C by the leads 89, 90, 9|. The corresponding windings 68, 69, 1|) of the Selsyn type repeater motor forming a part of the data speed responsive controller are also connected to the transmitter by the wires 92, 93, 94. The rotor 48 of the transmitter and the rotor 1| of the Selsyn type receiver are connected to a source of alternating current power as designated.

The searchlight is driven by the reversible mo tor E through the gears 65, 64, the shaft 63, gears 59, 69, and the shaft 6|, at the same time the Selsyn type displacement voltage controller is driven from the shaft 53 through the gears 58, 51 and the shaft 59. The gear ratios are such that the rotor 48 and the rotor 55 are at the same geared ratio to the telescope and searchlight respectively. When the telescope and light are in positional angular alignment the rotor 55 is at 90 from the field in the receiver C and a displacement to either side of agreement position, whether arising from movement of the light or from movement of the telescope produces a voltage across the terminals 95, 99 of the device C, which voltage through the amplifier AA energizes the motor E to drive the light in a direction to reduce the voltage again to zero.

However, the voltage at the terminals 95, 98

if applied to control the motor through the amplifier would give rise to jerky response of the motor, and the condition known as hunting and surging would be present. The use of my present invention permits of a control free from the ill effects of surge and hunt, and also permits of operating the searchlight in absolute agreement with the telescope.

The circuit operation is best understood by consideration of the amplifier input circuit shown in heavy lines. It will be seen that the amplifier input is composed of three separate and distinct components; a voltage from the displacement controller C, applied at terminals 95, 96, a voltage from the data speed responsive controller D, applied at points 8D. 8| and a voltage from the motor speed responsive controller applied at points 86, B1.

Now the voltages are designated as follows:

data speed The phases and magnitudes of the voltages es and es are determined by motor speed and data speed respectively, and the voltages applied at the respective terminals of the primary windings 18 and B4. The device D, which is positioned remotely from the transmitter B and may be adjacent the signal generator C and its associated devices, AA, F and E, consists of a Selsyn type repeater motor directly connected by the shaft 15 to a speed responsive device as disclosed in this application. A complete device is shown in Fig. 7. The rotation of the rotor 16 (counterpart of 24 of Fig. 5 and Fig. 7) in the flux of the primary winding 18 produces a voltage in the secondary winding 19 which varies in magnitude and direction as a function of speed and direction of rotation of the rotor 15. Likewise the motor speed responsive device F consists of the rotor 83 (counterpart of 24 in Fig. 5) which when rotated the field of the primary 84 produces a voltage in the secondary winding-85 which varies in magnitude and direction as a function of the speed and direction of rotation of the rotor 83 which is `driven from the motor E by the shaft 82.

The main amplifier AA is connected at its output terminals 99, |09, IUI, |02 to the reversible motor E having a field 66 and armature 61, power being supplied to the main amplifier at terminals ||1, H9. I have not shown they details of the ampliiier AA which may be of the electron and/or gas tube type, or may be of tubeless construction, such as shown in my copending application, now Patent No. 2,176,101 dated October 17, 1939, or of the type shown in Edwards Patent No. 1,985,982. However, the amplifier is preferably of a type which for a given value of input voltage at terminals 91, 98 produces a finite speed of motor rotation regardless of motor torque.

Now assume that the voltages applied to the windings. 19, 84 are of correct magnitude and phase, and that their relative polarities are such that:

(a) The voltage produced in 85 opposes (through the amplifier) the signal tending to drive the motor.

(b) The Voltageproduced in 19 is of polarity to drive the motor (through the amplifier) in the direction of rotation of the transmitter B.

(c) The voltage produced at the terminals 95, 96

is of such direction as to (through the amplifier) drive the motor in a direction to remove the displacement, that is, to bring the light into agreement, angularly with the telescope.

With the above polarity conditions We have at the amplifier input terminals 91, 98 a voltage as follows:

G0 data speed) are of equal magnitude and opposite scope by sufficient polarity and therefore cancel. Under this condition the system is operating under control of the relative displacement between the light and the telescope, the light lagging behind the teledisplacement to produce a voltage at 95-99 to drive the motor at the correct speed.

Suppose now that the voltage required at terminals Yi1-98 under this speed condition is pro- T() duced by a disagreement between the transmitter B and the displacement controller C of say 5. If now the voltage applied to the primary winding 1B is increased .in any suitable manner as by shifting the position of adjustable tap 13 on the secondary of a supply transformer 12, re-

sulting in an increase of the voltage supplied by winding 19, the relative angular position of the controlling and controlled objects will change, that is, the position of the controlled object will be advanced, since the difference of the speed voltages, es and cs, is no longer zero but now supplies a portion` of the operating voltage applied to terminals 9T, S8 of amplifier AA and therefore less disagreement voltage ed is required to make up the required amplifier input, which is substantially constant at a given operating speed. When, in increasing the voltage applied to primary 1B, a value is reached which causes voltage cs (produced in winding 19) to be higher than cs (produced in winding 85) by an amount corresponding to the voltage produced at 95-95 by a displacement. then the light will run in absolute agreement with the telescope and no displacement signal will be necessary to keep the motor running, the entire control voltage being supplied by the difference of the two speed voltages, es' and es. Obviously at values of the excitation of iield 'i8 other than this critical value, the controlled object will either lag or lead the controlling object, in the one case because the difference of the speed voltages is less than the total required operating voltage and in the other case because this difference is greater.

If from any steady condition, either at rest or while running at some finite speed, the displacement changes by the light lagging or leading with respect to the telescope, heavy damping components due to differences between es and es are impressed upon the amplifier. In fact the difference between the voltages es and es represents the rate at which the displacement is changing and opposes (through the amplifier) any displacement change.

The follow-up control in Fig, 9 is capable of great accuracy and stability and is permanent in its adjustments.

Fig. is a diagrammatic showing of a speed responsive device made in accordance with my present invention having three complete sets of windings, a primary composed of the coils iBS- |04 connected to the terminals Hit-H4, a secondary composed of the coils IE5-|56 connected to the terminals IIS- l I6, and a damper winding composed of the coils I'l--IIJ-lflS-Ili! connected to the terminals |l|-l|2 The primary coils I03--I04 are two pole and the secondary coils |05-|06 are two pole windings at right angles to the primary, the damper windings compose ay four pole winding having poles as shown and the primary and secondary and damper windings are all inductively non-reactive upon each other. The D. C. iiux produced by the damper winding drags the rotor and prevents motor torque being developed by the speed responsive controller which might produce detrimental effects when driven by a Selsyn type repeater motor. This specilic type of speed responsive generator, however, is not claimed herein, but in applicants divisional application, now matured into Patent No. 2,206,920, dated July 9, 1940, for Apparatus for electrical control.

Though I have shown my invention as embodied in preferred forms, and a system incorporating my invention as applied to driving a searchlight in accordance with a telescope, I do not desire to be limited thereby, inasmuch as the general system shown in Fig. 9 may be employed in any application where apparatus such as a gun or searclilight or steering mechanism is to be controlled angularly by systems.

Though I have shown specific apparatus for i1- lustration and description of the invention, I desire to be limited only by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

l. In a positional follow-up control system, in combination with a controlling and a driven obect, means for producing a signal from relative displacement between said controlling and said driven object, a rotatable sleeve of non-magnetic but electrically conductive material, an inner stationary iron core for said sleeve, means for driving said sleeve from said controlling object, two iield windings adjacent said sleeve arranged in quadrature, one of said windings being excited by alternating current, and a motor for driving said driven object controlled by the signal produced by the first said means combined with the output of the second of said windings.

2. In a positional follow-up control system, in combination with a controlling and a driven object, means for producing a signal from relative displacement between said controlling and said driven object, a rotatable sleeve of non-magnetic but electrically conductive material, an inner stationary iron core for said sleeve, said sleeve being rotated by said driven object, a set of two field windings adjacent said sleeve and arranged in quadrature, a second rotatable sleeve of nonmagnetic but electrically conductive material, an inner iron core for said sleeve, said second sleeve being driven by said controlling object, a second set of two field windings adjacent said second sleeve and arranged in quadrature, one winding in each of said sets being excited by alternating current, and a motor for driving said driven object controlled by the signal produced by the first said means combined with the outputs of the other windings of said sets of windings.

3. An electric transmission system including a transmitter and at least one receiver arranged to be capable of mono-periodic operation with respect to one another, comprising means for introducing into the control of the receiver a force which contains a component in magnitude proportional to the degree of positional displacement which may exist between the receiver and the transmitter director member, and means for introducing into said control .a further component which is a function of the difference in "Selsyn type data agreement between the transmitter receiver may be maintained when the displacement signal is zero.

4. In a positional control system, e, controlling object, a remotely located controlled object, an electrical positional data transmitter arranged for operation by one of said objects, a transmission line connected thereto, a signal generator actuated by said other object and connected to said line for generating a control signal proportional to the positional disagreement of said two objects, a receiver also connected to said transmission line to operate synchronously with said transmitter, generator driven by said receiver for obtaining a control signal proportional to the velocity of said receiver, driving means for said controlled object, and means for controlling said driving means jointly in accordance with said disagreement and said velocity signals.

5. The method of operation of a positional control system having a controlling and a controlled object, whereby the controlled object may be caused to lag or lead the controlling object by any desired amount, comprising generating a control signal proportional to the positional disagreement of said two objects, generating control signals respectively functions of the velocities of said two objects but which may be relatively varied, combining said last tvvo signals to obtain the difference thereof, applying said disagreement signal and the difference of said velocity signals jointly to a motor driving the controlled object, and adjusting the magnitude of at least one of said velocity signals so that the controlled object may be caused to assume the desired lag or lead over the position of said controlling object.

6. An electric transmission system including a transmitter and at least one receive;1 arranged to be capable of mono-periodic operation with respect to one another, comprising means for introducing into the control of the receiver a force which contains a component in magnitude proportional to the degree of positional displacement which may exist between the receiver and the Atransmitter director member, and means for introducing into said control a further component which is a function of the diierence in speed of the receiver and the transmitter director member but which is not zero when said speeds are the same, whereby lag or lead in the receiver with respect to the transmitter may be maintained.

7. The method of operation of a positional control system having a controlling and a controlled object, whereby exact synchronism as to both position and speed is maintained, comprising generating a control signal proportional to the positional disagreement of said two objects, generating control signals respectively functions of the velocities of said two objects lbut in which the signal from the controlling object is greater than the signal from the controlled object when said speeds are equal, combining said last two signals to obtain the diierence thereof, and applying said displacement signal and the difference of said velocity signals jointly to a motor driving the controlled object.

ALGER S. RIGGS. 

